It is often desired to intermix two fluids intimately, on a continuous basis. Such is the case when there is a primary fluid flowing through a pipeline, and it is desired to evenly disperse the second fluid into the first. Such intermixing is particularly difficult when there is very little mutual solubility between the fluids, e.g., such as exists with common petroleum oil and water.
Numerous devices to achieve intimate line mixing between two fluids have been known heretofore. Many line mixers are described in J. H. Perry, Chemical Engineers Handbook, Fourth Edition (1963), McGraw Hill Book Co., New York. One type is a jet mixer, wherein one of the liquids is pumped through a small nozzle or orifice into a flowing stream of other liquid. Such types of devices are generally only successful in liquids which have low interfacial tension, i.e., those that are miscible. Another type of mixer is one in which the liquids are flowed together simultaneously down a pipeline, and pass through a series of nozzles or orifice plates spaced apart along the pipeline. See for instance U.S. Pat. No. 3,856,270 to Hemker wherein a series of perforated plates having channels in their surfaces are placed in face to face contact within the fluid stream. Herbsman et al in U.S. Pat. No. 1,924,038 discloses an apparatus with a multiplicity of orifices and nozzles, to mix, divide, and induce a rotary motion in the fluid. Christenson et al in U.S. Pat. No. 2,802,648 discloses a combination of jet mixer and orifice plate mixer. After the fluids are intermixed, they are caused to flow downstream through a series of perforated plates mounted along a shaft.
Other mixers also are known, some of them quite elaborate, all with the goal of achieving good dispersions in a uniform manner. See for example U.S. Pat. No. 4,087,862 to Tsien and U.S. Pat. No. 3,582,365 to Lindsey. However, when mixing relatively crude or dirty materials it is a problem if a mixer is constructed of rather complicated passages, fragile passages, or very small passages. Such features create difficulty in obtaining uniform operating conditions, and can make the units difficult to maintain, and costly as well.
The present invention is particularly concerned with introducing and dispersing as very fine uniform droplets a small quantity of water into a flowing stream of petroleum oil, as described in my U.S. Pat. No. 4,335,737 for Apparatus and Method of Mixing Immiscible Fluids. In particular, the patented invention is aimed at dispersing small quantities of water in a fuel oil stream, becuase it has been found that doing such provides increased combustion efficiency and savings in energy costs. As is well known, the quantity of fuel which flows to a combustor can vary as a function of time. My related invention provides for the proper proportioning of the small quantity of water, according to the flow of fuel oil. But, to be effective, a line mixer, or emulsifier as it is called in my related application, must be capable of achieving good dispersion of the water at varying flow rates. In addition, the pressure drop through the mixer ought not to be so great as to necessitate exceptionally high pressures. Further, the mixer ought to be capable of operating with viscous liquids with substantial solid particulate content, as characterizes SAE No. 6 fuel oil. The prior art mixers are not well suited for this.
Another problem with many types of mixers in the prior art is that they require rather involved engineering calculations when the size of the unit is being changed. That is, if successful results are achieved in one size of mixer, the complexities of fluid dynamics must be taken into account if a larger or smaller unit is desired. Simple proportioning, as is well known to those skilled in fluid dynamics, will not often achieve the same results. Thus, since there is a desire that line mixers have different total flow capacities, it is desired that the design of a mixer be such that it is readily made to different scales.